Devices using network communications over wireless links are becoming increasing popular. Wireless links typically transmit data over radio frequency channels but may operate over other carrier frequency ranges, such as infrared. Most radio frequency based wireless networks are designed to operate in two basic modes: the infrastructure mode and the peer-to-peer or ad hoc mode. In the infrastructure (“IS”) mode, which is also sometimes referred to as the managed network mode, each wireless network node communicates with the other nodes through an access point (“AP”) node of the IS network. The access point functions as a bridge, repeater, gateway, and firewall between wireless nodes and wired nodes of the network. The access point may also apportion bandwidth to the wireless IS nodes to ensure the quality of the communications.
In the ad hoc (“AH”) mode, a wireless node communicates directly, i.e., in a peer-to-peer fashion, with other nodes within its RF range without going through an intermediate node such as the access point of the IS network. Ad hoc wireless network connections are useful when close-by users want to communicate with each other in places where no IS network exists, or when they fail to be authorized by the access point of an existing IS network.
At a given location, there may be an IS network coexisting with an AH network whose range overlaps with that of the IS network. Moreover, the IS wireless devices and AH wireless devices may try to communicate over the same frequency channel. The two networks, however, are disjoint in that the nodes in one network generally are not able to directly communicate with the nodes in the other network. When wireless devices of different networks try to transmit over the same channel, conflicts in bandwidth usage may arise. For example, in one scenario, a sales representative is waiting at an airport lounge to catch a flight. The airport has a public local area network (LAN) that supports an IS wireless network and has an access point in the lounge. To use the few remaining minutes before his flight takes off, he decides to download his email and some power point files from his corporate network over a wireless link through the airport's IS network so that he can work on his upcoming customer presentation during his long flight. Being short on time he negotiates with the airport's IS network some additional bandwidth for his session to allow him to complete his downloads quickly. In the meantime, a group of students who are located close to him and equipped with computers and wireless LAN cards start to communicate with each other wirelessly over an AH network that uses the same frequency channel as the airport's IS network. A computer of one of the students may attempt to transmit at the same time the sales representative's computer attempts to transmit, resulting in a conflict. When the two computers detect this conflict, both of them enter into a back-off state and try later to retransmit when the frequency channel is clear. As a result, the AH network formed by the students adversely affect the bandwidth guarantees promised to the sales representative by the IS network.